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Dennis Wright has hung up his gumboots after 17 years as the Northland Regional Council's farm monitoring manager, but he will not soon be forgotten.

The council says Mr Wright has left a dairy effluent reduction model that could prove to be an impressive environmental and economic legacy.

Trials had been completed over the last four years on farms at Brynderwyn, Hukerenui, Waipapa and Ngararatunua (near Ruatangata), while a range of initiatives promoted by Mr Wright had also helped improve water quality by significantly reducing farms' water use and discharges of treated effluent to water.

Collectively the four trial farms had reduced water use by roughly 15,000 cubic metres (15 million litres), and had cut the amount of wastewater generated by almost 16,800 cubic metres (16.8 million litres).

"The two best-performing farms in the trial reduced their water use by roughly half and the others by roughly a third," Mr Wright said.

"Data collected at two of the four farms showed that they also managed to cut the effluent volume generated by roughly half."

The dairy industry continued to spend many millions of dollars on projects aimed at mitigating adverse environmental effects and improving its image, and the trials proved that with a few simple, cost-effective changes, it was possible to tackle issues related to water extraction and point source effluent management.

"This not only improves environmental performance, but can result in significant reduction in on-farm operating costs," he said.

Central to the trials had been the use of water meters to measure actual use at different points around the dairy, installation of more water-efficient cleaning nozzles, and diverting as much clean stormwater as practicable away from the treatment ponds.

Other initiatives on some farms included changing from water to electric-driven yard backing gates, and using recycled effluent to clean their dairy yards.

Ken Finlayson, who milks 780 Friesians on 300ha at Ngararatunua, said since moving into a new dairy shed three years ago he had almost halved his water use, largely though changing nozzles on hoses, the farm dairy bridge and D-gate, by capturing plant wash water and recycling through a yard wash system.

"We're saving about 5.4 million litres of water per dairy season, which equates to usage of about 27 litres per cow per day on average," he said. Typical standard industry usage is about 70 litres per cow per day.

Apart from the obvious environmental benefits — it was much easier to be compliant without handling such large volumes of effluent — the fact that he would not need to pay for an additional effluent storage pond had saved him about $80,000.

Mr Wright said the the idea for the effluent reduction project stemmed from his own frustration that co-operative and willing Northland farmers could still find it difficult to comply with their resource consent conditions.